Method of making contact bodies of tungsten.



A. J. LIEBMANN & W. A. MEGRATH.

METHOD OF MAKING CONTACT BODIES OF TUNGSTEN.

APPLICATION FILED NOV. 20. I914.

1,155,426. Patented Oct. 5, 1915.

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UNITED STATES PATENT OFFICE.

ALFRED LIEBMANN AND WILLIAM A. MEGRA'IH, OF NEW YORK,-

Y., ASSIGNORS TO INDEPENDENT LAMP AND WIRE COMPANY, INC., OF NEW YORK, N; Y., A COB- PORATION or new JERSEY.

METHOD OF MAKING CONTACT BOIJIES OF TUNGSTEN.

Specification of Letters Patent.

/ Application filed November 20, 1914. Serial No. 873,087.

To all tokom it may concern:

'Be it known that we, ALFRED J. LIEBMANN and ZWVILLIAM A. MEGRATH, respectively of the borough of Manhattan, city, county, and

"State of New York, and of the borough of Brooklyn, county of Kings, city and State like purposes.

As set forth in the Patent No. 1,111,698

I granted September 22nd, 1914, to Alfred J.

ies of tungsten to a backing of other metal Liebmann, the metal Obtained by the invention covered thereby is suitable to be used for contacts for magnetos and similar devices where there is a frequent making and breaking of an electric current.

In the present application the claims are directed to the process and the claims to the product are contained in our co-pending application Serial No. 29,777, filed May 22nd,

1915, as a division of the present application in compliance with a requirement of the Patent, Oflice. y

In order to make the tungsten contact plate or disk suitable for such purposes, it is desirable and in some cases even necessary to fasten or secure it to another metal, which other metal is so shap d that it can be easily attached to the apparatus in whichthe contact element is to be used. The tungsten plate or disk maybe formed in any suitable way, for instance, it"may be out either from a plate of rolled tungsten or in cross sections from a rod or ingot of tungsten. The second metal as a rule is in the form and shape of a" tack and suitably shaped to fit into some'part which can be designed as the rec'eptacle for. the actual tungsten contact element.

It-has heretofore been considered impossible to join tungsten contacts or otherbodwithout using a third kind of metal to join the two together. It has been the practice to join the tungsten contact plate or disk, to the tack by meansof an auxiliary third metal different from the metals of the con tact' and support.

We have invented 'a process whereby ,we

can join the tungsten plate or disk to the tack without the aid of such an auxiliary third metal. That is, we fuse or weld the tungsten contact plate or disk directly to the holder or carrier or backing material, which is to be set into the apparatus and which as a whole can be described as a contact breaker.

By means of our invention an article is Patented 0ct. 5, 1915.

produced which is commercially superior to the articles used heretofore which latter necessitate a third kind of metal being interposed between the tungsten and carrier or supporting material, for it has the advantage of overcoming the objection thereto due to the presence of a third kind of metal of lower fusing point between the tungsten and the carrier metal, which might during the operation of the circuit breaker become hot, get soft and thereby make the tungsten contact lose connection from the carrier metal and thereby fall ofl. This danger is avoided by means of our invention in which the tungsten contact disk or plateis directly joined to the carrier metal which may be for instance iron or steel. The resulting element is, therefore, homogeneous, and can almost be said to consist of one solid piece, the two pieces of metal being joined directly together and forming one undivided unit. Furthermore our device is easier and less expensive to manufacture.

In the practice of our invention we place between the'two meta-ls a point or a multi tude of points of the same material, either steel or tungsten which will oppose when a current of electricity is passed through the two metals, a higher resistance to the passing electric current, and therefore reach a perature will be highest where the surfaces of the two metals to be joined. contact with the points or projections between them and thus cause the two metals to soften and weldtogether when the proper pressure is applied.- We have also found'that we can still heighten this effect by placing between the two metals, a chemical, which when the current is being passed and a high temperature is being reached, by its own chemical action, willintensify the heat, and at the same time polish and .clean the surfaces of the two metals in such a way that they stick to each other much better or much more intimately very high temperature locally. This temand form a composite body much easier than when simply joined without-this auxiliary chemical, which cleans the surfaces of any film of oxide or other foreign-material which might be present. This chemical is so selected that it at the same time has a deoxidizing action for both metals, and we ha ve found as most suitable for this purpose, alkali or alkaline compounds, especially potassium nitrite.

The reaction between potassium nitrite and tungsten, which is the example given. is very highly exothermic, once started. This can easily be shown by a very simple experiment. If a cold piece of tungsten is dipped into a fusion of potassium nitrite, the reaction begins slowly, but after a very short time the piece of tungsten becomes red hot. even if no outside heat is applied.

The fusion does not freeze, which it would do if the action were endothermic; on the contrary, it becomes even hotter by the reaction.

Referring to the drawings: Figure 1 is an elevation showing a single point or projection for welding the tungsten contact to the iron or steel base. Fig. 2, is a plan view of the supportin tack shown in Fig. 1. Fig. 3, is a side-e evation similartoFig. 1 with a plurality ofwelding points or projections as shown. Fig. 4, is a plan of the supporting tack shown in Fig. 3. Fig. 5, is

a side elevation of the supporting tack and tungsten plate having a multitude of welding projections on the head of -the tack. Fig. 6, is a plan view of the supporting tack shown in Fig. 5. Fig. 7, is a side elevation of the supporting tack and tungsten contact plate with powdered tungsten metal therebetween. Fig. 8,is a plan view of the supporting tack shown in Fig. 7 having thereupon powdered tungsten metal. Fig. 9, is a side elevation of the supporting tack and contact plate showing both the welding points and the powdered tungsten metal 1 therebetween. Fig. 10, is a plan view of the supporting tack with both the welding points or projections and the powdered metal tungsten thereupon shown in Fig. 9. Fig. 11, is a sectional view through the center of the supporting tack and contact plate showing a recess in the center of the contact plate and a projection in the upper surface of the tack. Fig. 12, is a plan of the uppersurface of the supporting tack shown in Fig. 11. Flg. 13, is a section 0 a supporting tack and contactplate in a position inverted from that shown in Fig. 11, with powdered tungsten metal shown in the recess. Fig. 14, is a. plan of the under surface of the tungsten plate or disk shown in Fig. 13. Fig- 15, is a. conventional apparatus used in the carrying out of-my process.

n the drawings, similar ref rence characters indicate like parts. K

1Q represents the tungsten contact plate or disk, 11 an iron or steel supporting'itlack' or base having a head'12 and ashanlg 13 depending therefrom; 14 represents""welding points and 15 powdered tungsten metal; 16 is a cavity or recess in the tungsten contact plates or disks.

Referring to Fig. 15, 20 represents" the upper electrode consisting of a rod of conducting material which is bent in a half circle and positioned in such a way asto come in contact with the center of the lower electrode 22, the two being pressed together by a suitable spring 24 or other suitable means. The upper electrode has a slight' re -fgo cess 21 in its center tohold the tungsten plate or disk 10 and thereby prevent itfrom sliding sidewise, and the lower electrode also] has a slight recess 24 in its center tohold the iron or steel supporting tack in place; 3 i Both electrodes are connected in circuit through'the terminals 30 which also connect in circuit with a source of power 31 a'"rheoj: stat 32, a measuring instrument 33 and a switch 34. The lower electrode is slida-bly mounted upon a fixed rod 40 and is sup; ported in itsupper position by a spring-24 situated between'the electrode and a collar 41 mounted upon the rod 40 and held in place by a set screw 42 to adjust its position 96 atmosphere which has a de-oxidizing act-ion. 10.6

We find hydrogen of special advantage,? which is almost obvious because it helpsito keep the two surfaces of the metal plates, 1 which are to be joined together, clean, and. prevents them from oxidizing. w t,.-.';1l0

We have found, however, that we cut.

carry out our process, not only in vacuu'mzor':

neutral atmosphere, but when using af'idefli oxidizing chemical, as described above,;=we; have succeeded in making a perfect weld 511x11 the open air, an operation which heretofores has never been performed and has been con-: sidered impossible. It is of advantage from?) several points of view to do this.- Flrst'the' operations can be carried .out much easier 1! than under theubells or other vessels, as it'lis' necessary when the work is carried out in mi neutral atmosphere or vacuum, andv second the electric current used can be moderated;

quite considerably as compared for instance T with an atmosphere of hydrogen, which-gas;

has a very high thermal conductivity Kandacarries away agood deal of the .heat which? is produced by the passage of the current." To make our invention more clearly understood and adaptable to persons skilled in the art, we will hereafter describe several.

ways how it can be performed. For example we shall speak of tungsten as the one .metal which will serve as the actual contact plate or disk of tungsten of a diameter of approximately is .05".

lVe have found several different ways to carry out the invention and according to .13 and the height of which these different ways, the tack to which the tungsten plate or disk willbe attached, has to be shaped differently. In the first case, this tack has a small protruding point or projection preferably in the center of the disk. Thispoint is preferably 'of conical shape and its point is naturally directly over the center of the tack. While welding the point the tungsten plate is brought down on to this point in such a way that its center is touched .by the point of the projection. plate in this position are brought between two electrodes which are suitably shaped as herein described. lVe now pass "an electric current through the tack and the projection and the tungsten plate which brings the projection and that portion of the metal of the tack and tungsten plate adjacent thereto to a fusing or welding temperature, and the .welding is completed upon compressing the two metals together. The iron or steel projection must be made of sufficient size to furnish enough fused material to fasten the tungsten plate to the tack. Care should be exercised not to make the projection too high, because in that case complete fusion would not take place and the two surfaces could not be pressed tightly together. In the proportionate junction, that is when using a tungsten plate of about 0.139" diameter and .05 in height, and a tack, the supporting head of which is of the same height, the height of the iron or steel projection on the tack should be about .1 and its diameter about .08.

Instead of using one point in the center of the tack, two or more of these points may be used. The projections should be smaller the larger their number, and it is an advantage to use very many of these points so The tack and the tungsten.

rent and by its fusing joins and welds the two materials together, is iron or steel. In the third case we use tungsten or other similar material to that of the contact plate or disk. \Ve could produce tungsten plates with a point the same as in the first case or a multitude of points the same as in the second case, but we have found that in some cases instead of fusing these points to the tungsten plate it is practicalto use a comparatively smooth tungsten plate, a comparatively smooth steel tack and place between the two some powdered tungsten which provides a multitude of points or projections which create a very high resist-.

For such purpose we have selected ance. a coarse grain tungsten powder. When the current is passed through the tungsten plate,

powder and tack in an arrangement of this kind, the tungsten powder-between the tWo is fused and unites the two plates into a uniform piece.

It is of great advantage to combine the second and third cases in such a way as to use the'steel plate with a multitude of .projecting points as described, and place on tli is ilate the tungsten powder as-mentioned. l/ e form combined piece results. WVe have also found that in some instances it is of Id-3 An additional high resistance therefor will exist and consequently a high temperature will result when the current passes which causes the metal to fuse and. flow into the recess filling it and causing the best bindmg in the center of the tack, or at the point where it is most desirable. In the case of ti en get a combined action and a uni a multitude of projections, a multitude of be arranged the opposite way,'but because of the different physical properties of the metals, the recess is preferably formed in the harder metal namely the tungsten, because it is easier to form a. recess than to form a point of suitable length.

We have found it of advantage to use a chemical of the properties described heretofore, for instance, powdered potassium nitrite, which we find to be most suitable for this purpose. The powdered material, in the case of the fixed point or fixed points, is simply strewn on the flat plate, upon which the other plate, which is provided with the projection, is lowered. ,The moment the current is passed, the projection begins to glow, the chemical around it starts its action, and while developing local heat through this chemical action, it is cleaning and softening the surfaces, thereby preparing it for the intimate junction which re- .sults the moment the metal, which is of hlgh resistance, fuses.

lVhen using tungstenmetal powder, we mix the tungsten powder with the potassium nitrite powder and place this mixture between the tungsten plate and iron or steel tack. In the last case, that is when the welding is carried out in the air, we find the use of our chemical very useful. If it is not used, the two plates have a tendency to break apart, although we have succeeded in a good many instances to join them without the use of the chemical.

When working in hydrogen a'current of about 14100 amperes is needed to thoroughly weld the two pieces together, in the first case, that is when a single projection is used. When tungsten powder is only used, a current of about 1200 amperes is needed.

When in addition to the tungsten powder the chemical is used, it is suflicient to use a current of about 1000 amperes and in the case when the process was carried out 1n the 0 en air, a current of about 700 amperes is su cient to cause an intimate junction of the two metallic plates.

lVhat we claim as new and desire to obtain by Letters Patent, is z- 1. The method of making electric contacts of tungsten which consists in securing a tungsten plate to a supporting base by electrically welding with a resistance increasing material between the tungsten plate and the supporting base.

2. The method of making electric contacts of tungsten which consists in securing atungsten plate to a supporting base by electrical resistance welding with metal powder between the tungsten plate and the supporting base.

8. The method of making electric contacts of tungsten by electrically heating the tungsten contact plate and the supporting back, having powdered tungsten metal between the same.

4. The method of making electric contacts of tungsten by simultaneously treating tungsten and the supporting met-ll with an exothermically reacting compound and'electrically welding the two metals together.

5. The method of making electric contacts of tungsten by simultaneously treating the tungsten and the other metal with'potas sium nitrite and welding the two metals togethcr.

(3. The method of making electric contacts of tungsten which consists in placing powdered tungsten between the head of the tack and a plate or disk of tungsten metal simultaneously treating the powdered tungsten and the adjacent surfaces of the tack and plate with potassium nitrite and welding the parts together.

8. The method of making electric contacts of tungsten by welding the tungsten contact plate to a supporting back, first strewing between the two, powdered tungsten metal mixed with powdered potassium nitrite.

9. The method of making an electric contact, which consists in preparing two surfaces, one a tungsten face plate and the other a support therefor, placing upon one of said surfaces one or more points of the same character of metal as the surface, pressing the whole together and passing an electric current therethrough.-

10. The method of making electric contacts of tungsten by heating the tungsten contact plate and the supporting back, having a mixture of powdered tungsten metal and a powdered alkali between the same, and holding the parts together under pressure.

11. The methodof making electric contacts of tungsten by electrically heating the tungsten contact plate and the supporting back, having a mixture of powdered metal i 'ngsten and an alkaline compound between -.he same, and pressing the one upon the other.

In Witness whereof we have hereunto set our hands at the borough of Manhattan, city and State of New York, this 19th day of November, 1914;. 1

ALFRED J. LIEBMAN'N. WM. A. MEGRATH.

In presence of GEORGE P. SCHOLL, C. C. BILLINGS. 

